U.S. patent application number 12/767100 was filed with the patent office on 2010-08-12 for capless multiaxial screw and spinal fixation assembly and method.
This patent application is currently assigned to X-SPINE SYSTEMS, INC.. Invention is credited to David Louis Kirschman.
Application Number | 20100204738 12/767100 |
Document ID | / |
Family ID | 37416181 |
Filed Date | 2010-08-12 |
United States Patent
Application |
20100204738 |
Kind Code |
A1 |
Kirschman; David Louis |
August 12, 2010 |
CAPLESS MULTIAXIAL SCREW AND SPINAL FIXATION ASSEMBLY AND
METHOD
Abstract
A spinal fixation assembly and capless multi-axial screw system
and method are shown. The assembly comprises a receiver having a
rotary lock which in one embodiment includes a plurality of
channels which urge and lock the elongated member to the screw
using a bayonet type connection.
Inventors: |
Kirschman; David Louis;
(Dayton, OH) |
Correspondence
Address: |
MATTHEW R. JENKINS, ESQ.
2310 FAR HILLS BUILDING
DAYTON
OH
45419
US
|
Assignee: |
X-SPINE SYSTEMS, INC.
Miamisburg
OH
|
Family ID: |
37416181 |
Appl. No.: |
12/767100 |
Filed: |
April 26, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11193523 |
Jul 29, 2005 |
7717943 |
|
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12767100 |
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Current U.S.
Class: |
606/279 ;
606/305 |
Current CPC
Class: |
A61B 17/7002 20130101;
A61B 17/7037 20130101; A61B 17/7032 20130101 |
Class at
Publication: |
606/279 ;
606/305 |
International
Class: |
A61B 17/88 20060101
A61B017/88; A61B 17/86 20060101 A61B017/86 |
Claims
1. A spinal fixation assembly comprising: a receiver having a bore
for receiving a screw having a threaded portion and a screw head
that is received in said bore, wherein said bore has an opening at
a first end of said receiver through which said threaded portion
and said screw head pass when said screw is received in said
receiver and a second opening at a second end of said receiver
through which only said threaded portion passes until said screw
head is received in a seat of said receiver; said receiver
comprising a receiving channel for receiving an elongated member
and a locking channel for locking said elongated member in direct
engagement with said screw when said receiver is rotated from an
unlocked position to a locked position such that when said receiver
is rotated from said unlocked to said locked position, said
elongated member moves in said bore and directly engages said screw
head; said receiver further comprising at least one camming surface
that cooperates with an opposing surface for defining said locking
channel, said at least one camming surface facilitates camming said
elongated member to urge said compression member to apply a
compressive force against said screw head.
2. The spiral fixation assembly as recited in claim 1 wherein said
locking channel spirals about an axis of said receiver.
3. The spiral fixation assembly as recited in claim 1 wherein said
locking channel and said receiving channel cooperate to provide a
bayonet connection between said elongated member and said
screw.
4. The spiral fixation assembly as recited in claim 1 wherein said
seat comprises a generally rounded or tapered seat associated with
said second end of said receiver, said screw head comprising a
rounded profile and received in said generally rounded or tapered
seat to permit said receiver to move polyaxially relative to said
screw after said screw is mounted into a vertebra.
5. The spiral fixation assembly as recited in claim 1 wherein said
bore comprises a diameter that is greater than a cross-sectional
dimension of said receiving channel and said compression member
comprises a diameter that is received in said bore.
6. A spinal fixation assembly comprising: a receiver having a bore
for receiving a screw having a screw head that is received in said
bore; and a compression member dimensioned to be received in said
bore and having a first end for receiving an elongated member and a
second end for engaging said screw head; said receiver comprising a
receiving channel for receiving said elongated member and a locking
channel for locking said elongated member to said screw when said
receiver is rotated from an unlocked to a locked position.
7. The spinal fixation assembly as recited in claim 6 wherein said
locking channel spirals about an axis of said receiver.
8. The spinal fixation assembly as recited in claim 6 wherein said
locking channel and said receiving channel cooperate to provide a
bayonet connection between said elongated member and said
screw.
9. The spinal fixation assembly as recited in claim 6 wherein said
bore comprises a generally rounded or tapered seat associated with
a coupling end of said receiver, said screw head comprising a
rounded profile and received in said rounded seat to permit said
receiver to move polyaxially relative to said screw after said
screw is mounted into a vertebra.
10. The spinal fixation assembly as recited in claim 6 wherein said
bore comprises a diameter that is greater than a cross-sectional
dimension of said receiving channel and said compression member
comprises a diameter that is received in said bore.
11. The spinal fixation assembly as recited in claim 6 wherein said
bore comprises a bore diameter that is greater than a
cross-sectional dimension of said receiving channel and said
compression member comprising a compression member diameter that is
greater than said cross-sectional dimension of said receiving
channel, but less than said bore diameter.
12. The spinal fixation assembly as recited in claim 6 wherein said
compression member comprises a second receiving channel, wherein
said receiving channel comprises a first axis and said second
receiving channel comprises a second axis, said second axis and
said first axis being generally parallel when said elongated member
is in said unlocked position and generally perpendicular when said
elongated member is in said locked position.
13. The spinal fixation assembly as recited in claim 6 wherein when
said receiver is rotated from said unlocked position to said locked
position, said elongated member becomes secured to said screw and
situated closer to said screw.
14. The spinal fixation assembly as recited in claim 13 wherein
when said receiver is in an unlocked position, said receiving
channel becomes generally aligned with a second receiving channel
in said compression member.
15. The spinal fixation assembly as recited in claim 6 wherein said
receiving channel is generally perpendicular to an elongated member
axis of said elongated member when said receiver is in said locked
position.
16. The spinal fixation assembly as recited in claim 6 wherein said
locking channel spirals from a first end of said receiver toward a
second end of said receiver.
17. The spinal fixation assembly as recited in claim 6 wherein said
locking channel defines a helix.
18. The spinal fixation assembly as recited in claim 6 wherein said
receiving channel extends from an end of said receiver in a
direction that is generally parallel to an axis of said receiver
and said locking channel extends at least partially about said axis
of said receiver.
19. The spinal fixation assembly as recited in claim 6 wherein said
compression member comprises a second receiving channel that
becomes generally aligned with said receiving channel when said
elongated member is received in said receiver and said first and
second receiving channels becoming generally perpendicular when
said receiver is rotated to said locked position.
20. The spinal fixation assembly as recited in claim 6 wherein said
receiver comprises at least one camming surface that cooperates
with an opposing surface for defining said locking channel, said at
least one camming surface camming against said elongated member to
move said elongated member against said compression member which,
in turn, applies a compressive force against said screw head in
response thereto.
21. The spinal fixation assembly as recited in claim 6 wherein said
receiver comprises a plurality of camming surfaces that cooperate
with a plurality of opposing surfaces, respectively, to define said
locking channel, said plurality of camming surfaces camming against
said elongated member to force said elongated member against said
compression member which, in turn, applies a compressive force
against said screw head when said receiver is rotated.
22. The spinal fixation assembly as recited in claim 6 wherein said
locking channel comprises a first locking channel area and a second
locking channel area; said receiver comprises a first camming
surface generally opposed to a first opposing surface to define
said first locking channel area and a second camming surface
generally opposed to a second opposing surface to define said
second locking channel area, said first and second camming surfaces
camming against said elongated member to force said elongated
member against said compression member which, in turn, applies a
compressive force against said screw head when said receiver is
rotated.
23. The spinal fixation assembly as recited in claim 22 wherein
said locking channel comprises a lock member associated therewith
for facilitating retaining said receiver in a locked position.
24. The spinal fixation assembly as recited in claim 23 wherein
said lock member comprises a detent or protrusion or a plurality of
detents or protrusions in said receiver and associated with said
locking channel.
25. The spinal fixation assembly as recited in claim 23 wherein
said lock member cooperates with an end wall of said locking
channel to define a locking area at which said elongated member is
locked when it is in said locked position.
26. The spinal fixation assembly as recited in claim 6 wherein said
receiving channel lies in a first plane that is generally planar
and said locking channel lies in a second plane that is
non-planar.
27. The spinal fixation assembly as recited in claim 26 wherein
said second plane spirals about an axis of said receiver.
28. The spinal fixation assembly as recited in claim 6 wherein said
locking channel extends in a direction that is non-axial relative
to an axis of said receiver.
29. The spinal fixation assembly as recited in claim 6 wherein said
screw head is generally spherical and said compression member
comprises a seat that is also generally spherical and dimensioned
to receive said screw head.
30. A spinal fixation assembly comprising: a receiver having a bore
for receiving a screw having a screw head and a receiving channel
in communication with said bore for receiving an elongated member;
and a compression member dimensioned to be received in said bore
and having a first end for engaging said elongated member and a
second end for engaging said screw head; said receiver comprising a
rotary lock for locking said elongated member to said screw.
31. A spinal fixation system comprising: a receiver having a bore
for receiving a screw having a screw head; and a compression member
dimensioned to be received in said bore and having a first end and
a second end; said receiver comprising an integral rotary lock for
locking an elongated member to said screw when said receiver is
rotated.
32. A method for securing an elongated member to a spinal column,
comprising the steps of: screwing a screw into a first spinal bone,
said screw having a screw head that is received in a seat of a
receiver having a bore through which threads of the screw may pass;
situating the elongated member into said receiver; and rotating the
receiver to fasten said elongated member onto said screw.
33. The method as recited in claim 32 wherein said method further
comprises the step of: situating said elongated member against a
compression member which engages said screw head to fasten said
elongated member to said screw when said receiver is rotated.
34. The method as recited in claim 33 wherein said method comprises
the step of: aligning a receiving channel of said compression
member with a receiving channel of said receiver before said
situating step.
35. The method as recited in claim 33 wherein said method comprises
the step of providing the compression member and receiver
pre-aligned prior to said screwing step.
36. The method as recited in claim 32 wherein said receiver
comprises a receiving channel and a locking channel, said method
further comprising the steps of: situating said elongated member in
said receiving channel; rotating said receiver so that said
elongated member becomes situated in said locking channel.
37. The method as recited in claim 36 wherein said method further
comprises the step of: aligning said receiver before said rotating
step.
38. The method as recited in claim 36 wherein said method further
comprises the steps of: screwing a second screw into a second
spinal bone, said second screw having a head that is received in a
seat of a second receiver having a bore through which threads of
the second screw may pass; situating said elongated member into
said second receiver; and rotating said second receiver to fasten
said elongated member onto said second screw after performing said
first rotating step, thereby fixing the relative positions of said
first and second spinal bones.
39. The method as recited in claim 38 wherein said method further
comprises the step of: aligning said receiving channel of said
receiver with a second receiving channel of said second receiver
before said second rotating step.
40. The method as recited in claim 32 wherein said method further
comprises the step of: repeating said method using a plurality of
screws having a plurality of retainers, respectively, and said
elongated member to secure a plurality of vertebrae together in a
fixed relationship.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of U.S. patent
application Ser. No. 11/193,523, filed Jul. 29, 2005, which is
incorporated herein by reference and made a part hereof.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to a capless multiaxial screw and
spinal fixation assembly and method, particularly useful for fixing
and/or aligning vertebrae of the spine. The invention permits
multiple angular orientations of an elongated member or rod with
respect to a screw that is screwed into a vertebra.
[0004] 2. Description of the Related Art
[0005] Various methods of spinal immobilization have been known and
used in the past. The preferred treatment for spinal stabilization
is immobilization of the joint by surgical fusion or anthrodesis.
This method has been known since development in 1911 by Hibbs and
Albe. However, in many cases, in particular cases involving fusion
across the lumbosacral articulation and where there are many levels
involved, pseudorarthrosis is a problem. It was discovered that
immediate immobilization was necessary in order to allow a bony
union to form. Post operative external immobilization, such as the
use of splints and casts, was a favored method of treatment,
however, as surgical techniques have become more sophisticated,
various methods of internal and external fixation have been
developed.
[0006] Internal fixation refers to therapeutic methods of
stabilization which are wholly internal to the patient and include
commonly known devices such as bone plates and pins. External
fixation, in contrast, involves at least some portion of
stabilization device which is external to the patient's body.
Internal fixation is now the favored method of immobilization
because the patient is allowed greater freedom with the elimination
of the external portion of the device and the possibility of
infection, such as a pin tract infection is reduced.
[0007] There have been numerous systems and methods developed in
the past for correcting and stabilizing and aligning the spine for
facilitating, for example, fusion at various levels or areas of the
spine, such as those devices are shown in U.S. Pat. Nos. 4,085,744;
4,269,178; 4,805,602; 5,466,237; 5,474,555; 5,891,145; and
6,869,433 B2. Bone screws with a polyaxial head are commonly used
in spine surgery today. They are used chiefly in the lumbar spine
and screwed into bone (pedicle) posteriorly. The head of the screw
is attached to the shaft of the screw by means of a ball and
socket. The top of the screw is machined into a ball, and the head
contains a socket into which the ball fits. The screw head further
contains a receiver for receiving a separate rod. The rod is
fastened to the screw head receiver via a threaded cap. The rod is
then fastened to screws placed in adjacent vertebrae thus providing
stabilization. The polyaxial head allows the rod to be placed in a
variety of angles with respect to the screw allowing conformance to
local anatomy.
[0008] When the threaded cap is tightened upon the rod, a
frictional pressure is transmitted from the threaded cap to the rod
thence to the top of the ball, thus locking the ball-in-socket and
preventing motion after tightening has occurred. This concept is
demonstrated in U.S. Pat. Nos. 5,466,237 and 5,474,555, which
illustrate this type of screw.
[0009] U.S. Pat. No. 5,466,237 to Bird et al. discloses a bone
screw having a spherical projection on the top of the bone screw.
An externally threaded receiver member supports the bone screw and
spinal rod on top of the spherical projection. An outer nut is
tightened onto the receiver member to press the spinal rod against
the spherical projection to accommodate various angular
orientations of the bone screw relative to the rod.
[0010] In another approach shown in U.S. Pat. No. 4,946,458 to
Harms, a spherical headed bone screw supported within separate
halves of a receiving member. The bottom of the halves are held
together by a retaining ring. The top of the receiver halves are
compressed about the bone screw by nuts threaded onto a threaded
spinal rod.
[0011] In still another approach taken by Harms et al. in U.S. Pat.
No. 5,207,678, a receiver member is flexibly connected about a
partially spherical head of a bone screw. Conical nuts on opposite
sides of the receiver member threaded onto a threaded rod passing
through the receiver. As the conical nuts are threaded toward each
other, the receiver member flexibly compresses around the head of
the bone screw to clamp the bone screw in its variable angular
position. One detriment of the systems in the two Harms et al.
patents is that the spinal rod must be threaded in order to accept
the compression nuts.
[0012] U.S. Pat. No. 6,869,433 discloses the use of a pedicle screw
assembly that comprises a screw having a head with a convex portion
and a receiver that receives the head. The receiver also receives
an elongated member, such as a spinal fixation rod. The receiver
has a concave portion which has a radius of curvature which is less
than the radius of curvature of the convex portion of the head
whereby to create an interference fit between the convex portion of
the head and the concave portion of the receiver. The device also
includes an internal nut and external nut that compresses the rod
against a pressure disc which in turn compresses the head convex
portion of the screw into the receiver concave portion and locks
the angular position of the receiver with respect to the screw.
[0013] One of the problems with the prior art devices is the number
of parts and components, especially those components that utilize a
threaded cap screw to secure the rod to the anchoring screw,
whether internal or external, to fix the rod relative to the screw.
Problems with the threaded fastener, that is, threaded cap or set
screw, are numerous and include risk of cap loosening, loss of cap
intra-operatively, cross threading, thread failure, failure of the
cap in driving instrument and limitations upon torque
application.
[0014] What is needed, therefore, is a system and method that
provide a lock or connection between the rod and screw without the
use of external nuts, screws, caps or threads of the type shown in
the prior art.
[0015] These and other objects and advantages of the invention will
be apparent from the following description, the accompanying
drawing and the appended claims.
SUMMARY OF THE INVENTION
[0016] The present invention improves the spinal fixation and the
locking between an elongated member or rod and a screw.
[0017] One object of the invention is to provide a system and
method that reduces or eliminates the need for external or internal
caps or screws to lock the relative position of a rod to a
screw.
[0018] Another object of the invention is to provide a simple
bayonet-type connection that eliminates the fixation systems of the
past and/or simplifies the spinal fixation procedure.
[0019] In one aspect, this invention discloses a capless multiaxial
screw comprising a screw having a threaded portion and a screw
head, a receiver having a bore for receiving the threaded portion
and a receiving channel for receiving an elongated member, the
channel further comprising a locking channel in communication with
the channel, a compression member for situating in the bore, the
compression member comprising a second receiving channel having a
first end and a second end and further associated with a first end,
and a receiving area associated with the second end for receiving
and engaging the screw head, the elongated member cooperating with
the compression member to lock the elongated member to the screw
when the elongated member is received in the first and second
receiving channels and the receiver is rotated from an unlocked
position to a locked position.
[0020] In another aspect, this invention discloses a spinal
fixation assembly comprising a receiver having a bore for receiving
a screw having a screw head that is larger than a diameter of the
bore, and a compression member dimensioned to be received in the
bore and having a first end for receiving an elongated member and a
second end for engaging the screw head, the receiver comprising a
receiving channel for receiving the elongated member and a locking
channel for locking the elongated member to the screw when the
receiver is rotated from an unlocked to a locked position.
[0021] In yet another aspect, this invention relates to a spinal
fixation assembly comprising a receiver having a bore for receiving
a screw having a screw head that is larger than a diameter of the
bore and a receiving channel for receiving an elongated member, and
a compression member dimensioned to be received in the bore and
having a first end for engaging the elongated member and a second
end for engaging the screw head, the receiver comprising a rotary
lock for locking the elongated member to the screw.
[0022] In still another aspect, this invention relates to a spinal
fixation assembly comprising a receiver having a bore for receiving
a screw having a screw head, and a compression member dimensioned
to be received in the bore and having a first end for engagement
with an elongated member and a second end for engagement with the
screw head, the receiver comprising a locking channel and a
receiving channel coupling the locking channels, the receiving
channel receiving the elongated member and the locking channels
cooperating to secure the elongated member to the screw when the
receiver is rotated.
[0023] In another aspect, this invention discloses a spinal
fixation assembly comprising a receiver having a bore for receiving
a screw having a screw head, and a compression member dimensioned
to be received in the bore and having a first end and a second end,
the receiver comprising an integral rotary lock for locking the
elongated member to the screw when the receiver is rotated.
[0024] In another aspect, this invention relates to a method for
securing an elongated member to a spinal column, comprising the
steps of screwing a screw into a spinal bone, the screw having a
head that is received in a seat of a receiver having a bore through
which threads of the screw may pass, situating the rod into the
receiver, and rotating the receiver to fasten the rod onto the
screw.
[0025] These and other objects and advantages of the invention will
be apparent from the following description, the accompanying
drawing and the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 is a fragmentary perspective view of a capless
multiaxial screw and fixation assembly mounted on a spinal column
having a plurality of vertebrae;
[0027] FIG. 2 is a perspective view of the system shown in FIG.
1;
[0028] FIG. 3 is an exploded fragmentary perspective view of the
system shown in FIGS. 1 and 2;
[0029] FIG. 4 is a fragmentary perspective view illustrating a rod
received in a receiving channel of a receiver;
[0030] FIG. 5 is a fragmentary plan view of the illustration shown
in FIG. 4;
[0031] FIG. 6 is a fragmentary view similar to FIG. 4, but showing
the receiver rotated approximately 30 degrees about its axis
relative to the rod;
[0032] FIG. 7 is a fragmentary plan view similar to FIG. 5 and
showing the receiver in the position illustrated in FIG. 6;
[0033] FIG. 8 is fragmentary perspective view showing the receiver
in a fully locked position;
[0034] FIG. 9 is a plan view similar to FIGS. 5 and 7 showing the
receiver in a fully locked position;
[0035] FIG. 10 is a view taken along the line 10-10 in FIG. 4;
[0036] FIG. 11 is a view illustrating the rod after it has been
received in the channel of the receiver and supported above a
bottom surface of a compression member;
[0037] FIG. 12 is a sectional view taken along the line 12-12 in
FIG. 8;
[0038] FIG. 13 is a fragmentary view showing the rod in
cross-section and in a fully locked position;
[0039] FIG. 14 is a fragmentary view illustrating various features
of the locking channels;
[0040] FIG. 15 is a plan view showing a compression member received
in a bore of the receiver and illustrating the aperture through
which a tool may be inserted to rotate the screw head before the
rod is positioned in a channel of both the receiver and the
compression member;
[0041] FIG. 16A-16E are various views of the receiver in accordance
with one illustration of the invention;
[0042] FIG. 17 is a sectional view of a compression member in
accordance with one illustration of the invention;
[0043] FIG. 18 is a fragmentary sectional view of another
illustration of the invention, showing a channel having walls that
are generally non-planar to define an intermediate area for loosely
capturing the rod;
[0044] FIG. 19 is a side elevation view of the embodiment shown in
FIG. 18;
[0045] FIG. 20 is a fragmentary sectional view that has been
rotated relative to FIGS. 18 and 19;
[0046] FIG. 21 is an elevational view rotated relative to FIG.
19;
[0047] FIGS. 22-24 are plan views illustrating rotational movement
of the receiver relative to the rod;
[0048] FIGS. 25-27 are side elevation views that generally
correspond to FIGS. 22-24, respectively, illustrating the receiver
in various positions, but with the rod removed for ease of
illustration and understanding;
[0049] FIGS. 28-30 are views similar to FIGS. 25-27, respectively,
illustrating the receiver in various rotational positions relative
to the rod as the rod is moved from a receiving position to a
locked position;
[0050] FIGS. 31-33 are fragmentary sectional views somewhat
enlarged and diagrammatic to simply illustrate the intermediate
capturing step of receiving area for loosely capturing the rod in
the receiver; and
[0051] FIG. 34 is a diagrammatic view which is presented for
purposes of illustrating various dimensions of the channels in the
receiver or the second illustrative embodiment.
DETAILED DESCRIPTION OF THE INVENTION
[0052] Referring now to FIGS. 1-3, a capless multi-axial screw and
spinal fixation assembly 10 and method are shown. The spinal
fixation assembly 10 comprises a screw 12 having a threaded portion
12a and a screw head 12b that in the embodiment being described,
has a rounded profile or curvature, as best illustrated in FIGS. 3
and 10-13. The screw head 12b comprises a hex female opening or
slot 12c for receiving a tool (not shown) for screwing the screw 12
into an aperture 14a of a spinal bone 14, such as a vertebra of a
spine.
[0053] As illustrated in FIGS. 1 and 2, one feature of the
invention is that it enables a user to fix a relative position of a
plurality of vertebrae, such as vertebrae 14, 16 and 18 in FIG. 1,
in a fixed and stabilized position.
[0054] The spinal fixation assembly 10 comprises a retainer or
receiver 20 having a generally cylindrical receiver wall 20c (FIG.
4) that defines an aperture or bore 22 that traverses or extends
along a receiver axis A (FIG. 11) the entire length of the receiver
20, as best illustrated in FIGS. 4, 10, and 12. The receiver 20
comprises a first end 20a and a second end 20b, and although not
shown, may comprise a chamfer 21 of about 45 degrees. It should be
understood that the receiver wall 20c defines a receiver seat 20d
toward the bottom of the receiver 20 (as viewed in FIGS. 10 and 15)
that is arcuate or curved in cross section. The receiver seat 20d
has a radius or curved surface R1 (FIG. 10). Note that a diameter
or distance D1 (FIG. 10) of bore 22 at the second end 20b of the
receiver or retainer 20 is slightly smaller than both a diameter or
distance D2 (FIGS. 7 and 10) of the bore 22 at first end 20a and a
diameter D3 (FIG. 12) of the rounded screw head 12b so that it
defines the receiver seat 20d (FIGS. 10 and 15) for receiving or
capturing the screw head 12b. In this regard, the screw head 12b
has an end 12b1 that is configured and dimensioned to be received
or captured in the seat 20d and that can be rotated or screwed
while in the bore 22 (FIGS. 10 and 15). The end 12b2 has a curved
or arcuate shape that generally complements the shape of the seat
20d to permit polyaxial and relative movement between the receiver
20 and screw 12.
[0055] As shown in FIGS. 3 and 11-13, the bore 22 receives the
threaded portion 12a of the screw 12 until the screw head 12b is
received in the seat 20d (as illustrated in FIGS. 10-13). It should
be understood that the seat 20d cooperates with the end 12b1 of
screw head 12b and permits the retainer or receiver 20 to move
polyaxially about a center of screw head 12b so that position of
the receiver 20 may be altered relative to the screw head 12b of
screw 12. This allows a user, such as a surgeon or physician, to
change the polyaxial position of the receiver 20 relative to the
screw 12 in order to adjust an angular position of an elongated
member or rod 24 relative to, for example, the vertebrae 14, 16 and
18 illustrated in FIG. 1. The rod 24 may be any suitable shape in
cross section, such as circular, hexagonal, octagonal, polygonal or
the like.
[0056] Note that the receiver 20 comprises a receiving channel or
slot 26 (FIG. 15) defined by wall surfaces 21a, 21b, 21c and 21d
(FIG. 4). The receiver 20 further comprises a lock, locking means,
locking channel, or rotary lock 28 (FIGS. 11 and 12) which is
integral with the receiver 20. In the embodiment being described,
the receiver 20 is manufactured of titanium and is machined to
provide the receiving channel 26, rotary lock 28 and the bore 22
using conventional machining techniques. Other potential materials
include biocompatible load bearing material, such as metals, metal
alloys, carbon fibers, composites, plastics or hybrid
materials.
[0057] In one embodiment, the lock 28 cooperates and is in
communication with the receiving channel 26 to provide a continuous
channel 30 for receiving the elongated member or rod 24. The lock
28 cooperates with the receiving channel 26 and urges rod 24 toward
the screw head 12b and vertebra, such as one of the vertebra 14-18
in FIG. 1, when the receiver 20 is rotated in a clockwise direction
(as viewed in FIG. 3). The continuous channel 30 comprises a first
channel 32, the channel 26, and the second channel 34. The lock 28
and continuous channel 30 provides a bayonet-type connection for
coupling or fixing the receiver 20, the rod 24 and screw 12
together in the manner described herein.
[0058] Note that the lock 28 comprises the first channel 32 and a
second channel 34 (FIGS. 12 and 13) that extend or spiral, as
illustrated in FIGS. 16A-16E, about the receiver axis A (FIG. 11)
of receiver 20. The first and second channels 32 and 34 generally
spiral or revolve from the first end 20a of receiver 20 toward the
second end 20b, as shown in FIGS. 10-13 and 16A-16D. Thus, in the
embodiment being described, the first and second channels 32 and 34
are non-linear and spiral or revolve in a general helix about the
axis A of the receiver 20. In the illustration, the channels 32 and
34 spiral or revolve in the same direction about the axis A, as
shown in FIGS. 16A-16D. Note that the channels 32 and 34 are in
communication with both the receiver bore 22 and receiving channel
26 of receiver 20. During operation, the channels 32 (FIG. 11) and
34 (FIG. 12) receive the rod 24 after it has been received in
channel 26 and urge or force the rod 24 toward the screw head 12b
and vertebra, such as vertebra 14 in FIG. 1, when the receiver 20
is rotated in a clockwise direction in the illustration being
described.
[0059] As illustrated in FIGS. 11 and 16A, the first channel 32 is
defined by a first surface or wall 20e, a generally opposing second
surface or wall 20g, and a third surface wall 20f that joins the
walls 20e and 20g in the receiver 20. A fourth surface or wall 20h,
a generally opposing fifth wall 20i, and a sixth surface or wall
20j that joins walls 20h and 20i cooperate to define the second
channel 34 (FIGS. 12 and 16D). Note that the walls 20e and 20g are
generally parallel and walls 20h and 20i are generally parallel. In
the illustration being described, the walls 20e and 20g and 20h and
20i are generally planar and have generally constant distance D4
(FIG. 13) and D5 (FIGS. 11 and 12) therebetween. However, in the
illustration described later herein relative to FIGS. 18-32, the
opposing walls 20e, 20g, 20h and 20i may be non-planar so that the
distance or dimensions D9 and D10 vary along the length of the
channels 32 and 34.
[0060] The channels 32 and 34 generally lay in planes P1 and P2
that are at the angles C (FIG. 14) and D, respectively, relative to
the axis A of the receiver 20. As described later herein, the walls
20e and 20h engage and cam against the rod 24 and force or urge it
downward (as viewed in FIGS. 10-15) in response to the rotary
movement of the receiver 20. In another embodiment described later
herein, the walls 20e and 20g and walls 20h and 20i may comprise a
curved or arcuate area and may cooperate to define an intermediate
rod capturing area, as described below relative to FIGS. 18-34.
[0061] As illustrated in FIGS. 4 and 11, note that the channel 32
is defined by the walls 20e, 20f, 20g and generally curved or
arcuate wall portion 50 that couples second surface or wall 20g to
wall surface 21b (FIGS. 4 and 16A) of channel 26. The generally
curved arcuate wall portion 50 also generally defines an
intersection or transition from the receiving channel 26 to the
first channel 32 of lock 28. The channel 34 is defined by wall
portions 20h, 20i and 20j and a third generally curved or arcuate
wall 52 that joins the wall 20i to wall surface 21d (FIGS. 4 and
16C). The wall 52 provides an intersection or transition between
channel 26 and the second channel 34. Notice that the wall portions
20f (FIG. 11) and 20j (FIG. 12) also each have a radius of
curvature that generally complements the radius of curvature or
circumference of the rod 24 so that when the rod 24 is moved from
the unlocked position (illustrated in FIGS. 4, 5, 10 and 11) to a
locked position (illustrated in FIGS. 8, 9, 12 and 13), the rod 24
is received and positioned against the wall surfaces 20f and 20j as
shown.
[0062] The spinal fixation assembly 10 may further comprise a
compression member 40 (FIGS. 3 and 17). The compression member 40
comprises a wall 40a that defines a second generally U-shaped
receiving channel 42. The compression member 40 also comprises a
frusto-conical seat or concave area 41 (FIGS. 10 and 17), defined
by a tapered wall or surface 40b, that engages the rounded shape of
the end 12b1 (FIG. 3) of screw head 12b. Although not shown, the
spinal fixation assembly 10 could be provided without the
compression member 40, so that the rod 24 would engage the screw
head 12b directly, for example, when the receiver 20 is rotated as
described later herein.
[0063] The compression member 40 comprises a length D6 (FIGS. 3 and
17) and a diameter D7 (FIG. 17) dimensioned to be received in the
bore 22 as shown. The second channel 42 defined by wall 40a
comprises a bottom surface 40c. The second channel 42 is generally
U-shaped in cross section and has a width or dimension D8 (FIGS. 3,
7 and 17) and bottom surface 40c comprises a radius of curvature R5
(FIG. 17) that generally complements or is slightly larger than the
circumference D9 (FIG. 3) of the rod 24.
[0064] During operation, the compression member 40 is urged
downward (as shown in FIGS. 10-13) in response to the rotary
movement of the receiver 20. The rod 24 engages the bottom surface
40c (FIGS. 12 and 17) of the second channel 42 of compression
member 40. This in turn causes surface 40b to engage and apply a
compressive force against the end 12b1 of screw head 12b as the rod
24 is driven in the downward direction (as viewed in FIGS. 10-13)
and into the second channel 42. This movement forces and compresses
the seat 20d against the end 12b2 of screw head 12b of the receiver
20, thereby locking the screw head 12b to the rod 24 and fixing the
relationship of the receiver 20 relative to the screw head 12b.
[0065] Note that the compression member 40 (FIG. 17) also comprises
a bore or aperture 43 defined by wall or seat 40d. The bore 43 has
a dimension or diameter D10 (FIG. 17). A surgeon or physician may
insert a tool, such as a hex head screwdriver (not shown), through
channel 26, through bore 22 of receiver 20 and through the bore 43
and into the hex female opening or slot 12c (FIG. 15), for example,
to tighten or loosen the screw 12. Thus, it should be understood,
as illustrated in FIG. 15, that the hex female opening or slot 12c
of screw head 12b is accessible after the screw 12 is inserted
through the bone 14 and compression member 40 is situated in the
bore 22.
[0066] Referring back to FIGS. 10-16E, the receiving channel 26
(FIG. 11) of receiver 20 extends from a first end 20a of receiver
20 in an axial direction and lies in a plane P3 (FIG. 15) that is
generally planar and extends downward along the axis A (as viewed
in FIG. 14). In contrast, the lock 28 defined by the channels 32
and 34 revolve, spiral or extend laterally or radially at distances
that are generally constant relative to axis A and that vary, such
as increase, relative to the first end 20a of receiver 20. As
mentioned earlier, each of the channels 32 and 34 spiral in a
general helix downward from the receiving channel 26 and about the
axis A of the receiver 20 as shown in FIGS. 10-13 and 16A-16D. Note
that the channels 32 and 34 lay in the planes P1 and P2 (FIG. 14),
respectively, that intersect axis A at the predetermined angles
indicated by double arrows C and D. The predetermined angles C and
D are acute angles in the embodiment being described.
[0067] As shown in FIGS. 16A and 16B, the channel 32 is inclined
relative to a radial line of receiver 20 at a third angle
(indicated by double arrow E in FIG. 16A) relative to the first end
20a. Channel 34 is also inclined relative to a radial line at a
fourth angle F (FIG. 16B). Although not shown, it is contemplated
that other designs, configurations or arrangements of channels 32
and 34 and the lock 28 may be provided, such as channels (not
shown) that extend about axis A, but that do not spiral and/or that
are not at the inclined angles E and F, such as channels that
extend at distances that are generally constant relative to the
first end 20a.
[0068] An operation or method regarding this illustration will now
be described. As illustrated in FIGS. 3-9 and 15, the screw 12,
together with receiver 20 are screwed into vertebra 14 during which
a physician or surgeon screws the threaded portion 12a of screw 12
in the aperture 14a of the vertebra 14 using a tool (not shown),
such as a hex wrench or screwdriver (not shown), that is inserted
through channel 26, bore 22 and bore 43. In one embodiment, the
receiver 20, screw 12 and compression member 40 may be provided in
a pre-assembled unit prior to surgery, so no assembly is required
by the physician. The screw 12 is screwed substantially all the way
into vertebrae 14, but is left with space between the receiver 20
and vertebrae 14 so that an angular or polyaxial position of the
receiver 20 may be adjusted or changed during the operation.
[0069] The channel 26 of receiver 20 and second channel 42 of
compression member 40 are provided or arranged in a common plane
P3, as shown in FIGS. 4, 5 and 15. The surgeon then places the rod
24 into the channels 26 and 42 and adjusts the multi-axial or
polyaxial position of the receiver 20 relative to the rod 24. As
mentioned earlier, the channel 26 and bores 22 (FIG. 10) and 43
(FIG. 17) provide a continuous opening or area 49 through which the
physician or surgeon may insert a tool, such as a hex tool, to
turn, rotate and/or tighten or loosen the screw 12 in the desired
direction prior to placing the rod 24 into channel 26. At this
point, the rod 24 remains in an unlocked position.
[0070] Note that the rod 24 is supported by and between the arcuate
or curved wall portions 50 and 52, which causes the rod 24 to be
situated above the bottom surface 40c of the second channel 42 of
compression member 40, as illustrated in FIGS. 10 and 11. Note that
the arcuate or curved wall portions 50 and 52 each comprise a
radius of curvatures R2 (FIGS. 11, 14 and 16a) and R3 (FIGS. 13 and
14), respectively, that generally complements or is larger than a
radius of curvature or circumference of the rod 24, as illustrated
in FIGS. 11 and 13.
[0071] The camming or bayonet type action of the rotary lock 28 on
receiver 20 forces the rod 24 in an axial direction parallel with
axis A of receiver 20 when the receiver 20 is turned or rotated
with a tool, such as a screwdriver (not shown), placed in channel
26, as illustrated in FIGS. 6 and 7. This rotary movement or action
forces the rod 24 downward (as viewed in FIG. 10) and into the
channels 32 and 34. As the receiver 20 is rotated further, as shown
in FIGS. 8 and 9, the walls 20e and 20g (FIG. 11) of channel 32 and
walls 20h and 20i (FIG. 12) of channel 34 act upon, force or urge
the rod 24 downward (as viewed in FIGS. 10-13) and into the second
channel 42 of compression member 40 until it engages the surface
40c of compression member 40. As the receiver 20 is rotated
further, the rod 24 urges the compression member 40 toward the
screw head end 12b1 and forces wall 40b of the compression member
40 against the screw head 12b of screw 12 with a compressive force
which causes the screw head 12b to become fastened or locked to the
rod 24, thereby fixing the receiver 20 and rod 24 to the screw
12.
[0072] It should be appreciated that when the rod 24 is in the
locked position shown in FIGS. 8, 9, 12 and 13, the rod 24 engages
wall surfaces 20e, 20f, and 20g of channel 32 and surfaces 20h, 20i
and 20j of channel 34 and surface 40c of second channel 42. The
wall or seat 40d of compression member 40 engages screw head 12b.
These surfaces cooperate to retain rod 24 in the locked position.
The surfaces 20f and 20j comprise a radius of curvature R4 of about
.phi.0.100-.phi.0.130 inch. A raised detent portion or bump 59
(which is only shown in FIG. 13 for ease of illustration) may be
provided in each channel 32 and 34, as shown in FIG. 13 relative to
channel 32. The detent 59 is provided to facilitate retaining the
rod 24 in the locked position.
[0073] Thus, as illustrated in FIGS. 1, 2 and 4-9, a surgeon may
use one or a plurality of spinal fixation assemblies 10 during a
spinal fixation procedure. For example, the surgeon may use a
plurality of receivers 20 and screws 12 with one rod 24, as
illustrated in FIGS. 1 and 2. In the illustration, the surgeon
screws the screws 12 into a plurality of vertebrae, such as
vertebrae 14, 16 and 18 illustrated in FIG. 1, and generally aligns
the channels 26 of receivers 20. The surgeon then inserts the tool,
such as a hex tool (not shown), through bores 22 and 43 and into
female slot 12c in screw head 12b and screws the screw 12 until the
bottom 20b of the receiver 20 engages or is proximately located
against its respective vertebra.
[0074] If the compression member 40 is being used, compression
member 40 is located in each bore 22 of each receiver 20 and
generally aligns the channels 42 and 26, as illustrated in FIGS. 4,
10 and 15. It should be understood that when the spinal fixation
assembly 10 is in the unlocked position, the channels 26 and 42 are
generally parallel or lie in the common plane P3 as shown in FIG.
15. The rod 24 is then placed in channel 26, whereupon it becomes
supported by walls 50 and 52 (FIG. 11). This causes rod 24 to be
supported slightly above the bottom 40c of the second channel 42 of
receiver 20, as mentioned earlier and as illustrated in FIGS. 10
and 11.
[0075] At this point in the procedure, the surgeon aligns the rod
24 in the receiver 20 to the desired position relative to the
spine, vertebrae and other receivers 20 that are being used. He
positions the rod 24 and polyaxial or angular position of each
receiver(s) 20 relative thereto. It should be understood that the
screws and position of the vertebrae, such as vertebrae 14-18,
relative to each other may also be adjusted. Once the bones 14-18
are adjusted and angular or polyaxial position of each receiver 20
is adjusted, the surgeon locks each receiver 20 to rod 24 by
rotating or turning the receiver 20 with a tool, such as a
screwdriver (not shown), placed in slot 26. This causes the
receivers 20 to become fixed or locked onto their respective screws
12 and the spinal bones or vertebrae 14-18 (FIG. 1) to become
aligned and fixed into the desired position.
[0076] It should be understood that before the rod 24 is placed in
the receiving channel 26 and the receiver 20 is rotated, the
surgeon may tighten one or more screws 12 to a tighter or fixed
seated position by situating the tool, such as a hex wrench (not
shown), through the aperture 43 (FIG. 15) defined by the wall or
seat 40d of the compression member 40 and into the hexagonal female
slot 12c in the screw head 12b. After the screw 12 is tightened to
the desired tightness or torque, the surgeon places the rod 24 into
the channels 26 and 42 (FIGS. 4, 5, 10 and 11) of the one or more
of the receivers 20 being used.
[0077] As mentioned, the surgeon rotates the receiver 20 about its
axis, as illustrated in FIGS. 3, 6 and 7 using a tool, such as a
screwdriver (not shown), in the clockwise direction, as illustrated
in FIGS. 6 and 7. During this rotation of receiver 20, the
compression member 40 and rod 24 do not rotate. As alluded to
earlier, walls 20e and 20g (FIG. 11) and walls 20h and 20i (FIG.
12) urge the rod 24 toward the bottom of channels 32 and 34 and
urge the rod 24 to move downward (as viewed in FIGS. 10 and 12)
toward the surface 40c or bottom of the second channel 42 where it
engages the surface 40c, as illustrated in FIGS. 4-9 and 10-13. The
rod 24 is also supported by and compresses against the surface 40c
of compression member 40. The wall or seat 40d is caused to engage
the screw head 12b.
[0078] Thus, when it is desired to lock the receiver 20 and the
screw 12 to the rod 24, the surgeon rotates the receiver 20 in the
clockwise direction, as illustrated in FIGS. 6 and 7, using the
conventional tool, such as a regular screwdriver. The receiver 20
is rotated until it is moved from the unlocked to the locked
position, as illustrated in FIGS. 8, 9, 12 and 13. Note that in the
locked position, the rod 24 is received and engages the walls 20f
and 20j associated with the ends of channels 32 and 34,
respectively.
[0079] Thus, it should be understood that when receiver 20 is
rotated, the walls 20e and 20h provide the camming force necessary
to cam and urge the rod 24 against the receiver 20. This, in turn,
causes the surface or wall 40b of receiver 20 to compress and lock
against the end portion 12b2 (FIG. 3) of screw head 12b. The wall
40b of compression member 40 cooperates with the curved seat
defined by wall 20d (FIG. 10) and traps or locks the screw head 12b
to the rod 24.
[0080] As illustrated in FIGS. 8, 9, 12 and 13, notice that the
channel 26 lies in an imaginary plane that is generally
perpendicular to the imaginary plane in which the second channel 42
and an axis of rod 24 when the receiver 20 is in the locked
position.
[0081] It should be appreciated from the foregoing that the
receiving channel 26 is in communication with the channels 32 and
34 of lock 28 and that the lock 28 cooperates with the rod 24 to
not only lock the rod 24 to the screw 12, but also to fix a
position of the vertebrae 14, 16 and 18.
[0082] When it is desired to unlock the rod 24 from the screw 12,
the surgeon simply rotates the receiver 20 in a counterclockwise
direction in the illustration and reverses the procedure.
[0083] Referring now to FIGS. 18-34, another illustrative
embodiment is shown. Those parts that are the same as the parts
relative to FIGS. 1-17 have been labeled with the same part number,
except that the part numbers in the embodiment described in FIGS.
18-34 have a prime mark ("'") associated therewith. The FIGS. 31-34
are diagrammatic enlarged sectional views for ease of
illustration.
[0084] Note in the embodiment in FIGS. 18-34, the receiver 20'
comprises channels 32' and 34' that each have a cross-sectional
dimension that varies over the length of the channels 32' and 34'
to provide an intermediate holding area 60b where the rod 24' is
loosely captured in the channels 32' and 34'. The channels 32' and
34' each have an introducing area 60a, an intermediate holding or
receiving area 60b and a locking area 60c. For ease of illustration
and description, the receiving area 60b will be described relative
to channel 32'; however, it should be understood that the channel
34' in the second illustration comprises substantially the same
configuration.
[0085] It should be appreciated that the intermediate holding area
60b in the channels 32' and 34' enable an intermediate step between
initial rod 24' insertion and final rod 24' locking. In other
words, this is a rod 24' capturing step during which the rod 24' is
loosely captured in the receiver 20', but it is not rigidly locked
into place against screw 12' yet. This allows the surgeon greater
ease and flexibility when he adjusts the screws 12' position with
respect to the rod 24' while the rod 24' is in place. For example,
the surgeon may move the screws 12' closer together (compression)
or In the illustration being described, the intermediate capturing
step is accomplished by rotating the receiver 20' partially, such
as approximately 30 degrees in the illustration as shown in FIGS.
23, 26 and 29, which forces the rod 24' from the introducing area
60a into the intermediate holding area 60b.
[0086] The introduction area comprises an associated dimension D13
(FIG. 34) and the locking area 60c has an associated dimension D14
(FIG. 34). The intermediate holding area 60b has an associated
intermediate dimension D15 (FIG. 34) between the wall 62 and second
wall 64 that is slightly larger than the diameter of the rod 24'
and the dimensions D13 and D14 associated with the introduction
area 60a and locking area 60c, respectively. It is dimensioned to
accommodate the rod 24' and to capture the rod 24' loosely so that
the rod 24' can easily slide between the walls 62 and 64 and is not
locked. This facilitates the surgeon adjusting a position of the
screws 12' in vertebrae, such as vertebrae 14'-18', relative to a
position of the rod 24. Once the screws 12' are adjusted to the
desired position, the physician or surgeon may then lock the
receiver 20' onto the screw 12' by inserting a tool, such as a
screwdriver (not shown), into the slot 26' and rotate the receiver
20' in the clockwise direction as illustrated in FIGS. 22-30.
[0087] In the illustration shown in FIGS. 31-34, the channel 32' is
defined by a wall 62, a generally opposing second wall 64 and a
joining wall 63 that joins walls 62 and 64 as shown. Note that
unlike the embodiment described relative to FIGS. 1-17, the wall 62
has a first wall portion 62a, a second wall portion 62b and an
intermediate wall portion 62c that couples the wall portions 62a
and 62b as shown. The opposing channel wall 64 comprises the first
wall portion 64a, a second wall portion 64b and an intermediate
wall portion 64c that couples the first and second wall portions
64a and 64b as shown. In this regard, note that an intersection 66
is defined between the wall portions 64a and 64c. A second
intersection 68 is defined between the wall portion 62b and 62c as
shown. The intersections 66 and 68 generally define an entrance to
the intermediate holding area 60b. The intermediate wall portions
62c and 64c cooperate to define the intermediate holding area 60b
which receives the rod 24' and loosely captures the rod 24' in the
receiver 20'.
[0088] The channels 32' and 34' are configured such that they
comprise or define the introduction area 60a for receiving the rod
24' in the receiver 20', as illustrated in FIGS. 22, 25 and 28. The
first wall portion 64a provides a ramp 64a1 for directing the rod
24' into the intermediate holding area 60b when the receiver 20' is
rotated about 20-40 degrees as shown in FIGS. 23, 26 and 29. As
shown in the illustration, the wall 62 and 64 are not generally
planar and have areas, such as intermediate wall portions 62c and
64c that are curved or recessed to facilitate defining the
intermediate holding area 60b.
[0089] During a surgical procedure, the surgeon may make the
desired adjustments of the rod 24' relative to the screws 12' and
vertebrae 14'-18' while the rod 24' is loosely captured in the
intermediate holding area 60b. The surgeon then uses the tool, such
as a screwdriver (not shown), to rotate the receiver 20' to the
locked position shown in FIGS. 24, 27 and 29. Similar to the
embodiment described earlier herein relative to FIGS. 1-17, the
receiver 20' urges or forces the rod 24' from the intermediate
holding area 60b to the locking area 60c. The rod 24' becomes
situated in the locking area 60c, whereupon the rod 24' becomes
locked therein. Note that the distance or dimension D12 (FIG. 8)
between the second wall portions 64b and 62b is substantially the
same or may be smaller than the diameter of the rod 24'. As the
receiver 20' is rotated in the clockwise direction in the
illustration being described, the wall 62 slightly deflects upward
(as viewed in FIG. 31, for example) to permit the rod 24 to be
captured and locked in the locking area 60c. Note that a portion of
walls 62, 63 and 64 comprises various radii of curvature R5-R9
having the illustrative dimensions or ranges of dimensions set
forth in the Table I below. For example, the radius of curvature R8
generally corresponds to the cross sectional circumference of the
rod 24' so that the rod 24' becomes captured in the locking area
60c. As in the prior illustration, the detent 59 (FIG. 33) may be
provided in channels 32' and 34' to further facilitate retaining
the rod 24' in the locking area 60c.
[0090] Advantageously, this system and method facilitates providing
a locking receiver 20 that reduces or eliminates the need for
threading, internally or externally.
[0091] Advantageously, the immediate holding areas 60b of channels
32' and 34' of the second embodiment are dimensioned and configured
to facilitate locking the rod 24' onto the screws 12' while
permitting ease of adjustment between the receiver 20' and the rod
24' when the rod 24' and receiver 20' are situated in the
intermediate holding area 60b', as illustrated in FIGS. 23, 26 and
29.
[0092] In the embodiments being described, the rod 24, screw 12,
receiver 20 and compression member 40 are all made of titanium
alloy. Other materials may be used such as metals, metal alloys,
carbon fibers, composites, plastics or hybrid materials.
[0093] For example, the screw 12 may have a length D11 (FIG. 3)
ranging from 10 mm-60 mm, and the receiver 20 may have a diameter
D12 (FIG. 8) ranging between 2 mm-10 mm. The compression member 40
may define the second channel 42 having the width D8 ranging
between 2 mm-12 mm. The channels 32 and 34 may comprise dimensions
D5, D6 (FIGS. 3 and 17) ranging between 2 mm-10 mm. It should be
understood, however, the other shapes and dimensions may be used
without departing from the true spirit and scope of the
invention.
[0094] Advantageously, this system and method provide a capless
multiaxial screw which eliminates the need for caps or screws or
threads of the type used in the prior art. This system and method
combine a very simplified yet effective means for locking an
elongated member or rod 24 to a screw 12 and spinal bone in the
manner described and shown herein.
[0095] While the apparatus, system and method herein described, and
the form of apparatus for carrying this method into effect,
constitute several illustrative embodiments of this invention, it
is to be understood that the invention is not limited to this
precise method and form of apparatus, and that changes may be made
in either without departing from the scope of the inventions, which
is defined in the appended claims.
* * * * *